[sledge] Allow global variables as function names

Summary:
Some called functions are represented in llvm as a global variable
with e.g. external linkage, and so they do not appear as
'functions'. It is still valid to call such functions, though the
analyzer does not know their definitions.

Reviewed By: bennostein

Differential Revision: D17725609

fbshipit-source-id: 333d19c0d

sledge/src/llair/frontend.ml

@@ -778,7 +778,7 @@ let pp_code fs (insts, term, blocks) =
 
 let rec xlate_func_name x llv =
   match Llvm.classify_value llv with
-  | Function -> Exp.reg (xlate_name x ~global:() llv)
+  | Function | GlobalVariable -> Exp.reg (xlate_name x ~global:() llv)
   | ConstantExpr -> xlate_opcode x llv (Llvm.constexpr_opcode llv)
   | Argument | Instruction _ -> xlate_value x llv
   | GlobalAlias -> xlate_func_name x (Llvm.operand llv 0)